Motor control unit

Abstract

A motor control unit includes a PWM count changer that when, out of all possible combinations of any two of three phases, at least one of the combinations has a difference in PWM count less than a threshold value, changes a PWM count of at least one of the two phases of the at least one of the combinations for each of PWM periods within a current control period, without changing the total of the PWM counts of the at least one of the two phases within the current control period, such that each of the combinations has a difference in PWM count greater than or equal to the threshold value.

What is claimed is: 
     
       1. A motor control unit for controlling a three-phase electric motor on a basis of PWM signals that are generated for each of a plurality of PWM periods included in a current control period, the motor control unit comprising:
 a PWM count generator that generates PWM counts of three phases for each current control period; 
 a PWM count setter that sets the PWM counts of the three phases generated for a specific current control period by the PWM count generator, as PWM counts of the respective phases for each of the plurality of PWM periods within the specific current control period; 
 a PWM count changer that when, out of all possible combinations of any two of the three phases, at least one of the combinations has a difference in PWM count less than a threshold value, changes the PWM count of at least one of the two phases of the at least one of the combinations for each of the plurality of PWM periods within the specific current control period, without changing a total of the PWM counts of the at least one of the two phases within the specific current control period, such that each of the combinations has a difference in PWM count greater than or equal to the threshold value; and 
 a PWM signal generator that generates the PWM signals for the respective phases for each of the plurality of PWM periods, on the basis of the PWM counts that are set for the respective phases for each of the plurality of PWM periods within the specific current control period and that are changed by the PWM count changer. 
 
     
     
       2. The motor control unit according to  claim 1 , wherein
 the PWM count changer changes one of the two phases that have the difference in PWM count less than the threshold value, without changing the total of the PWM counts of the one of the two phases within the specific current control period, such that each of the combinations has the difference in PWM count greater than or equal to the threshold value. 
 
     
     
       3. The motor control unit according to  claim 1 , wherein
 the PWM count changer changes both the two phases that have the difference in PWM count less than the threshold value, without changing the total of the PWM counts of each of the two phases within the specific current control period, such that each of the combinations has the difference in PWM count greater than or equal to the threshold value.